System and method for landing airplanes



Ot. 8, 1940. w. M. HAHNEMANN Er AL 2,217,404

SYSTEM AND METHOD FOR LANDING'AIRPLANES Original Filed April 26, 1954 y2'0 the courseso as to iiyY approximately parallel Figjl`diagrammatically"'illustrates Yin plan' a 45 sensitivity ,untilv landingin London, which will ever, as already explained in the foregoing, this45 I' Patented Oct. 8,1940 51V" n Y* f` d UNITED "STATES N lP., snr,o1-FICE Walter Max Hahnemann, Berlin-Marienfelde,

and Ernst` Kramar, Berlin-Tempelhof, Germany, assignors to C. LorenzAktiengesellschaft, Berlin-Tempelhof, Germany, acompany Originalapplication April 26, 1934, Serial' No.. Y,

722,470. Divided and'this application November 19, 1937, Serial No.175,439. In Germany May, 10, 1933 -3 claims. (01.250--115 The presentinvention vis a divisional from that to do on account of' theextraordinarilyy yhigh described in thecopendingU. S. Patent applisensitivity'of modern receivers. cation Ser. No. 722,470, led on April 26,1934, The" inventionrel-ates to a undamental'- i`m vfor System forlanding airplanes, and relates to provement 'of the slip-way beaconmethod. f l'cf an, improvement upon such arrangements. cording `to theinvention, the `beginning of the 5 It is well known .for the .purpose of'facilitatlanding is indicated by-a radianthpattern which'` ing4 thelandinggof airplanes to employ so-called also serves tor Ydefine an"equal intensityA Zone,

slip-way beacons which radiate a torus-shaped while the indication ofthefield intensity'which bundle of ultrashort electromagnetic waves atexists at the momentof reception ofthe addia certain angle tol thegroundsurface. The landtional 'signal indication 'is employedto :determine g.,

ing may be so eifected'that the airplane descends the'actual landingpath. f

' on a curve of constant field intensity. However, 'The-invention willbe more readily understood this method'involvesthe disadvantage that thefrom the following" description inconjunction curves of constant iieldintensity are too steep with the'accompanyingdrawing, in "whi'ch: inmajor heights, While tooflat in minor heights AFig. ll'shovvsanelevation cfa landing ground immediately in fronti of the point. atwhich the Fig. 2' -diagramrnatically"illustrates a receiv` airplanetouches ground within the airport. ingjarrangement according to theinvention,

Consequently, anairplane flying in majorheights adaptedto beused'iri-anAairp`leme`, whilel must at first descend rather steeply, while on FigfBschematically demonstrates an indicate reaching minor heights near theground change ing device for use inlaniairplane, v

tothe ground surface. 'I lie pilot is notin a directional beacon'foruse'withth'e glide path# position to continue the flight with idlemotor, as a` marker 'beacon'.

vbut is, compelled to give full power justbefore Referring t`o Fig. l1,the referencenuinerals touching theground. The unduly high speedl in fl'to 5 designate different` ^curves ci equaleld the actuallandingmoment asa-result thereof intensity, either of a we llknovm obliquelyV upa5 iscritical in many cases. In lorder to overcome wards directed bundle `ofl rays, of two intermit` this disadvantage, propositionshave been made,tentlykeyed bundles of raysv for obtaining azone .Y according to lwhichvthe airplane should intersect of equal intensity, or ofa"toruseshapedradiationv different curvesgeachvofwhich having an equaldiagram'. The invention is applicable to all field intensity, instead ofdescending on v one methods in connection withthe aforesaid types, "30

curve of constantiield intensity-V Forreliably while in case of need,Le., in casetwo Akeyed t realizing the above-saidmethod, it has hithertobundlesare not used, the l, direction determinabeen .necessarytoA ensurethat the transmitter tion must be '.eifected "by-additional means,` ramaintainsits power continuously constant, and pre'ferred'one 'of vwhichis'rnore'fully described that the receiver always has the samesensitivity. hereafter. The course line of the airplane is- 35 Thisrequirement mayrelatively easy be fullled designated B in the drawing;on the transmitter side by` supervising not only The method' hithertoemployed' is based on the transmitter, but alsothe transmitter field'.the fact that the airplane, which linv vthe 4first y On the receivingside, however, considerable dif-v instanc 'arrives horizontally on itsguiding course 40 `iculty is experienced, as .the sensitivity of theline' B, remains on this tcourse in the bundle of 40 Y receiver mustremainr the. same over a longer rays until it reaches'th'e eld intensityinwhich period of time. To. give van kexample in a Berlin it "mustdescend. As soon' as a'predeterminejd t to London flight, the,receiverwhich has to be deiiectionof the indicating device of the reiadjusted in vBerlin must maintain a constant ceiver is reached, theairplane descends. Howi,

take place several hours after.r It is, of cou-rse, requires vacontinuous `constancyvvith respectto possible to disconnect the receiverduring the thesen'sitivity of the receiver: if' journey, but uponre-insertion before the actual Y According to thelinvention, the pointat which landing in London it. must have the same sensithe landingshouldbe commenced Vis givenby ;v

tivity. In will easily'be seenthatthis isnot easy anfadditional` signal.indication y(i, which. is die' f rected perpendicularly, or obliquelyupwards. This additional indication may either be given acoustically orby wireless. The airplane flies on horizontally until it reaches thepoint 1, at which it receives the indication 6. It then descends frompoint 'I so that the deflection of the indicating device remains thesame as it was at the moment of the arrival of the signal indication 6.The curves 3, 4 and 5 are intersected at the points 8, 9 and I0 in orderto obtain a particular landing path subsequent to the receipt of theindication. Thisis obtained for instance in such a manner that thesensitivity of the indicating device of the receiver is varied independence upon the time elapsed from the moment in which saidindication was received,'or by shifting the scale of thein'dicatingdevice. It is now immaterial whether the indicating instrument indicatestwo or six points on the scale, i. e., if the sensitivity ofthe receiverhas been changed or not. It is by no means necessary that this change islinearly elected, on the contrary, it may be performed according to any`arbitrarily chosen rule. In other words, the landing curve may beoptionally designed in response to the intersecting points 1 to l0', soas to be accommodated to the airport conditions and to the type ofairplanes.

The Figs. 2 and 3 diagrammatically illustrate suitable equipments forrealizing the above disclosed idea. These equipments are simple meansadapted to be added to known devices. A shunt resistance or a seriesresistance may be connected to the indicating device, the magnitude ofsaid resistance being varied in dependence upon time, e. g., by a watchor the like. Means are thereby provided which connect said resistance tothe indicating device from the moment in which the signal indication wasreceived.f Referring to Fig. 2, E designates the receiver mounted on theairplane, and J the indicating device which indicates the landing pathand which is connected to the output side of the receiver E. A variableresistance P is shunted to the indicating device J, and the slidablecontact S of said resistance is shifted dependent upon time inaccordance with a certain rule from vthe moment in which the signalindication was received. It will also be possible to connect theresistance P in series with the indicating device J.

Furthermore, a particularly constructed indicating instrument asillustrated in Fig. 3 may be employed. The pointer Z is controlled bythe output circuit of the receiver in the well known manner; However,contradictory to the known arrangements in which the scale is xed, thescale Sk is moved, e. g., upwardly, in dependence upon time by any wellknown means (not shown) from the moment in which the signal indicationis received. Nevertheless, the pilot must navigate the airplane so, thatthe pointer Z continuously remains on the same point of the scale, onthe zero line, for instance.

The additional signal indication may be given by means of devices whichare in themselves well known, and arrangements for indicating thelanding ground boundaries are readily adaptable for this purpose. In thesimplest case a parabolic reflector may be employed which concentrates abeam of electromagnetic rays perpendicularly or 'obliquely upwards. Inaccordance with a novel feature of my invention I propose to employ'anarrangement which'produces a zone of equal intensity, particularly suchanr arrangementl which operates by means of vertical polarization. Suchan arrangement is described for example in U. S. Patent 2,028,510 issuedto Ernst Kramar January 21, 1936, which shows a vertical dipole whichcontinuously is fed by one transmitter, and two dipoles acting asreilectors. Fig. 4 shows such an arrangement together with a plan of thefield pattern produced thereby. These reflector dipoles `are alternatelymanipulated according to one of the known methods, for example in theA-N-rhythm. Thus in the well known manner a zone of equal intensity isobtained, that is by the fact that the circular radiation diagram of themiddle dipole continuously fed by the transmitter is alternatelydistorted so as to be displaced to one side and then to the other sidein a pattern of oblate shape as more fully set forth in the abovementioned patent. If .an airplane overflies such an arrangement, thereception on this airplane decays because the transmitter is operatingwith vertical polarization. The moment of decay is extremely sharplydened so that it may be employed as the said additional indication andpossibly for the automatic release of a suitable scale-moving orshunt-adjusting mechanism, which may be used in the arrangements ofFigs. 2 or 3, in order to change the sensitivity of the indicatingdevice in dependence upon time.

It is also possible to employ a plane of radiation instead of a bundleof rays, this plane being penetrated by the airplane. These arrangementsare preferably such that two transmitters are installed at twodiagonally opposite corners of the airport, each transmitter providingtwo sides of the airport with such planes of radiation. If `an acousticindication is employed, then suitable directing means may be used forthe sound transmitters or sound transmitting combinations.

What is claimed is:

1. The method of landing airplanes which comprises radiating a shortwave field of electromagnetic energy at an angle to the ground,radiating two further vertically polarized elds upwardly and outwardly,said polarized fields having a zone of substantially zero intensity,employing the relative eld strengths of'said two fields lto determinethe direction of night of the airplane, employing the zone of zerointensity formed by the vertical polarization of said further elds todetermine a region of reference in space, obtaining an'indication of theintensity of said short wave field at a .point in said determined regionin space, and thereafter employing said indication as a referencestandard with which to compare the short wave eld intensitiessubsequently encountered in landing said airplane within said short waveeld.v

2. An airplane landing path system comprising means for radiating ashort wave glide path eld having equal field strength surfaces obliquelyinclined with respect to the ground to produce glide paths terminatingat a particular landing point, means for radiating two distinguishableelectromagnetic signals with substantially vertical polarization inupwardly and outwardly extending radiationpatterns which mutuallyintersect to define a zone of equal intensity to providek for lateralguidance of said airplane, said signals having aninherent zone ofsubstantially zero intensity, said last mentioned means being arrangedsothat the zone of equal intensity is in line with said landing point, andbeing spaced from said landing point a distance such that said zone` ofzero intensity resulting from the substantially vertical polarization ofsaid electromagnetic signals intersects one of said equal field strengthsurfaces of said short Wave field at a location suitabie'for commencingthe descent of an airplane along said equal field strength surface.

' 3. A system as claimed in claim 2, wherein said means for radiatingtwo distinguishable signals comprises a vertical` dipole, means forfeeding Waves to said dipole, and a plurality of variably effectivereflectors for variably distorting the patterns radiated by said dipole.WALTERMAX HAHNEMANN. ERNST KRAMAR.

